The Wall Street Journal reported US Secretary of Transportation Pete Buttigieg issued a warning over potential air travel disruptions ahead of a deadline for C-Band compliant altimeters to be retrofitted to aircraft.

Buttigieg reportedly told the newspaper there is a risk of flights being delayed or cancelled if airlines do not complete upgrades by a deadline of 1 July.

Despite the politician’s warning, the Federal Aviation Authority (FAA) stated more than 80 per cent of the US’ domestic airline fleet and about 65 per cent of the international were equipped with altimeters which could operate safely in the 5G C-Band environment as of 23 June.

Verizon and AT&T delayed planned C-Band launches due to concerns over interference with altimeters, with several flights disrupted once the operators began limited deployments.

An FAA representative told Mobile World Live (Mobile World Live) a final airworthiness directive (AD) required airlines to revise their flight manuals to prohibit low-visibility landings after 30 June unless the retrofits were completed.

A representative from Verizon told MWL the operator plans to fully-employ its C-Band spectrum from 1 July.

“As we’ve said from the beginning, C-Band wireless operations and aviation can safely coexist, something that’s been proven in the US and around the globe.”